It was intended to build additional C18 Class locomotives in anticipation of increased traffic with the extension of the North Coast Line to Mackay. By 1920 the plan had been revised and resulted in the design of the C19 class. They were the largest conventional type locomotives to operate on QR.

The class was originally used for heavy Mail Train work and important North Coast Line traffic. They were eventually displaced from Mail Train working by B18¼ class engines.

Initially the class was restricted to working only as far as Bundaberg on the NCL but this was gradually extended north to Bowen. They did not regularly work beyond Mackay. Roma and Wallangarra were their limits in the West and South. Two of the class were based at Rockhampton, four at Maryborough and the remainder shared between Mayne and Willowburn (Toowoomba). They were regularly used on goods trains between Brisbane and Toowoomba and also on the Darling Downs.

N°702 entered traffic in December 1923 and was named “Centenary” as it was the hundredth engine constructed by Ipswich Shops.

A number of modifications were made over the years. The early engines had a large regulator dome and another smaller one for the safety valves similar to the B17 class. Those built from 1926 onwards had a boiler with only one small dome that contained both regulator and safety valves. Earlier engines later received this type as they became due for re-boilering.

The engines suffered from a number of defects and were prone to cracked frames. As their condition deteriorated and with the introduction of modern engines and later DEL for heavy traffic, the engines were relegated to lesser duties and most were withdrawn during the 1950s. Three engines that had been written off the books were returned to service for short periods in the late 1950s to overcome motive power shortages at that time.

N°800 was retained at Maryborough as a stationary steam plant for some years after being written off in April 1956.

Several C19 tenders were kept in a pool at Ipswich after their engines had been withdrawn. These tenders were then fitted temporarily to overhauled (C17/B18¼/BB18¼) engines that were ready to return to service but their respective tenders were not yet available

The last engine in service was N°700 at Toowoomba and was written off the books in February 1964.This engine was preserved and is now at Ipswich Workshops.